Thermal ink jet printers have experienced great commercial success since they were invented back in the early 1980's. Modern day thermal ink jet printers give users high speed printing capabilities along with near photographic quality color reproduction, all for a very low price. These attributes have made a high quality thermal ink jet printer an essential part of a home or office computing system.
In recent times, users have found that the thermal ink jet printer can be used not only to print text and numbers from word processing programs and spreadsheets, but can also be used to print images they have downloaded from the Internet, or even print their own photographs from pictures they have taken with their digital camera. In addition, users are now able to print off their own personalized catalogs, annual reports, newspapers and magazines-all using their ink jet printer in the comfort and convenience of their home or office.
This increase in the amount of material printed by a printer has resulted in a trend in the printer industry towards replenishable printing systems. One example of a replenishable printing system is an "off axis" printing system, where the supply of ink in the print cartridge is replenished via another ink supply, typically located remotely to the print cartridge but connected via tubing or the like. Such replenishable printing systems allow the print cartridge to be used for a longer period of time than what has been conventionally done in the past, where the print cartridge was typically thrown away after the ink supply was exhausted.
While such replenishable printing systems can result in a lower total printing cost to the user, such systems have raised new problems that, left unaddressed, may actually result in a great deal of inconvenience and additional expense to the user. One such problem is that the print cartridge of the ink jet printer can reach the end of its useful life and fail to print properly during a critical printing operation. While this failure may be proceeded by a diminished print quality, this may not be noticed by the user at all, or at least not until the print cartridge fails to print reliably and it is too late to go out and purchase a replacement print cartridge. Of course, these failures often seem to occur at the worst possible moment, usually the day a big deadline looms or a big presentation is due.
While some attempts have been made to notify a user that the replenishable ink supply is running out of ink, these attempts do not solve the problem caused by a print cartridge failure independent of the amount of available ink, since a printer with a print cartridge at the end of its useful life will not print properly, or at all, even if there is an adequate supply of ink.